/**
 * Copyright (C) 2011 Whisper Systems
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package com.appspot.eusms.util;

import com.appspot.eusms.sms.SmsTransportDetails;

public class EncryptedCharacterCalculator extends CharacterCalculator {

    private CharacterState calculateSingleRecordCharacters(int charactersSpent) {
        int charactersRemaining = SmsTransportDetails.ENCRYPTED_SINGLE_MESSAGE_BODY_MAX_SIZE - charactersSpent;

        return new CharacterState(1, charactersRemaining, SmsTransportDetails.ENCRYPTED_SINGLE_MESSAGE_BODY_MAX_SIZE);
    }

    private CharacterState calculateMultiRecordCharacters(int charactersSpent) {
        int charactersInFirstRecord = SmsTransportDetails.ENCRYPTED_SINGLE_MESSAGE_BODY_MAX_SIZE;
        int spillover = charactersSpent - charactersInFirstRecord;
        int spilloverMessagesSpent = spillover / SmsTransportDetails.MULTI_MESSAGE_MAX_BYTES;

        if ((spillover % SmsTransportDetails.MULTI_MESSAGE_MAX_BYTES) > 0)
            spilloverMessagesSpent++;

        int charactersRemaining = (SmsTransportDetails.MULTI_MESSAGE_MAX_BYTES * spilloverMessagesSpent) - spillover;

        return new CharacterState(spilloverMessagesSpent + 1, charactersRemaining, SmsTransportDetails.MULTI_MESSAGE_MAX_BYTES);
    }

    @Override
    public CharacterState calculateCharacters(int charactersSpent) {
        if (charactersSpent <= SmsTransportDetails.ENCRYPTED_SINGLE_MESSAGE_BODY_MAX_SIZE) {
            return calculateSingleRecordCharacters(charactersSpent);
        } else {
            return calculateMultiRecordCharacters(charactersSpent);
        }
    }
}
